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(11) | EP 0 301 697 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | A method and apparatus for producing a deformed pipe liner of tubular cross-section. |
| (57) A thermoplastic pipe liner (L) is initially formed in a cylindrical shape with a
diameter slightly larger than the internal diameter of the pipe (80). The liner (L)
is temporarily deformed at an elevated temperature to a different, U-shaped cross-section,
to reduce its overall cross-sectional dimension to facilitate insertion into the
pipe (80) to be lined. Once inserted, the pipe liner (L) is reheated to the crystallization
temperature of the thermoplastic material to cause the liner (L) to return to its
original cylindrical shape. Pressure within the liner (L) is also increased in two
stages to cause the liner (L) to conform to the interior surface of the pipe (80).
After expansion, ends of the liner (L) which extend beyond the pipe (80) are flared
into engagement with the pipe flanges (82). For lining pipe normally containing in
service fluid under pressure, the liner (L), after insertion into the pipe (80), can
be mechanically reformed to engage the interior wall of the pipe (80). The normal
service pressure is then used to maintain the liner (L) in its generally cylindrical
shape over the time necessary to completely relieve the stresses in the liner (L)
tending to cause the liner (L) to return to its deformed shape. |